This invention relates to a gateway system for connecting an existing telephone network utilizing a common channel signaling system to an IP (Internet Protocol) network.
In channel (or circuit) control for an existing telephone network utilizing a common channel signaling system, high reliability against occurrence of failure is required. In order to satisfy such a requirement, use is made of a technique in which signal transfer points or signal paths are switched so that signal processing is not interrupted even upon an occurrence of a failure. It is noted here that the common channel signaling system is a system in which a signal channel is provided in addition to a plurality of communication channels so that control signals for the communication channels are transmitted and received by the signal channel as a single data channel exclusively for the control signals. For example, a common channel signaling system No. 7 (SS7) is used in a carrier network.
On the other hand, development has been made of a gateway system for connecting the existing telephone network and an IP (Internet Protocol) network. The gateway system generally includes a plurality of media gateways. By the use of such a gateway system, various services on the IP network become available through the existing telephone network.
The above-mentioned gateway system further includes a media gateway controller (MGC) which terminates a No. 7 signal as a control signal of the common channel signaling system No. 7. The media gateway controller (MGC) controls a corresponding media gateway through the IP network to make the corresponding media gateway establish a communication path between the existing telephone network and the corresponding media gateway.
The above-mentioned media gateway controller (MGC) controls a plurality of media gateways. The media gateway controller serves as a node for carrying out call control and connection control and is therefore required to have a high reliability. On the other hand, upon occurrence of a failure, it is not possible to straightforwardly use a technique of switching the media gateway controller as a faulty node to another node as a new node.
This is because a particular communication channel between an exchange and the media gateway is identified by a destination point code (DPC) and a circuit (or channel) identification code (CIC). Therefore, the new node having a different point code (PC) can not identify the particular communication channel. Thus, the new node does not have a call status of the particular communication channel.
Upon occurrence of a failure in the media gateway controller itself or in a No. 7 network link or the IP network connected to the media gateway controller, call control for all channels controlled by the media gateway controller will be lost.